The present invention relates to the processing of semiconductor wafers. More particularly, the present invention relates to an improved apparatus for processing semiconductor integrated circuits. Merely by way of example, the present invention is illustrated for an oxidation furnace, but it will be recognized that the invention has a wider range of applicability.
Semiconductor integrated circuits currently being manufactured follow ultra high density (e.g., about 0.5 to 0.35 micron) design rules, and circuits manufactured in the near future will follow even smaller design rules. As device size decreases and integration increases, the demands on fabrication and corresponding equipment are increasing.
For example, one important step in the fabrication of modern semiconductor devices is forming oxides with defined thicknesses and quality. Fabrication of such devices often requires accurate control of oxide thickness. Techniques for growing an oxide, such as silicon dioxide (SiO2), include using low temperature processing in a high pressure environment or using high temperature processing in an atmospheric environment. It is recognized that the control of temperature, pressure and process gases in the furnace system is often important in controlling growth and quality of the oxide.
In an oxidizing furnace, the process gases may include, for example: oxygen (O2), hydrogen (H2) or water vapor (H2O), nitrogen (N2), trichloroethane (TCA) or Trans LC or hydrogen chloride (HCl), and argon (Ar). It is desirable that the leakage of process gases to or from the furnace system via pipes is minimized.
Leakage of process gases causes uncertainty as to flows necessary for controlled oxide growth. Also, process gas leakage may cause instability in the furnace system, possibly adversely affecting the growth or quality of the oxide. Leakage of process gases including TCA, for example, also may be environmentally undesirable.
Further, leakage of process gases from joints in the pipes connected to the oxidizing furnace may result in increased corrosion in the piping. The corrosion caused by such leakage often undesirably introduces impurities into the oxide being grown. Preventing oxide film quality degradation due to impurities from the corrosion is very important in producing devices that need to meet specified requirements. This corrosion also often involves increasing the amount of cleaning required to maintain the piping to the furnace system. In cases of extreme corrosion, the equipment or the piping may need to be replaced. Often time-consuming, the cleaning and/or replacement procedures constitute a serious, albeit necessary, interruption in the manufacturing of integrated circuits. Such an interruption in the continuous production of substrates in the manufacturing line may have a serious economic impact. Reducing total unproductive time increases the total number of wafers produced. Thus, it is desirable that leakage of process gas be minimized as efficiently and economically as possible.
From the above, it is seen that an improved apparatus for use in processing semiconductor wafers that economically and effectively minimizes process gas leaks is needed.
According to a specific embodiment, the present invention provides an apparatus for use with a semiconductor processing system having process gases or liquids through piping having a flat flange. The apparatus includes an O-ring, and a tube having an inner diameter and a flange at an end of the tube. The flange has an inner edge adjacent the inner dimension and an outer edge defining an outer dimension of the flange. The flange also has a level difference between the inner edge and the outer edge, where the inner edge is flat to contact the flat flange of the piping to permit smooth flow of the process gases or liquids through the piping and the tube. Also, the level difference provides the flange the capability to accommodate the O-ring between the flat flange and the outer edge of the flange. The apparatus further includes a fastening mechanism that tightly fastens a joint of the flat flange, the O-ring and the flange, to prevent leakage of the process gases or liquids from the joint.
According to another embodiment, the present invention provides a method of preventing leakage of process gases or liquids from a joint of external piping and piping in a semiconductor processing system. The method includes installing as the external piping a tube. The tube has a flange shaped to accommodate an O-ring. The method also includes providing an O-ring for use with the flange, and fastening the O-ring between the flange and the piping with a fastening mechanism to prevent leakage of process gases or liquids from the joint.
Yet another embodiment provides a retrofit to existing external piping. The present method includes additional steps of removing external piping from the joint, and machining the external piping to form the flange shaped to accommodate an O-ring. Accordingly, the installing step uses the machined external piping as the tube.
A further embodiment provides an apparatus for processing semiconductor substrates. The apparatus includes an internal housing having conduits for dispersing process gases or liquids into the internal housing. The internal housing is capable of providing heat for the processing of substrates. The apparatus also includes an outer encasement surrounding a portion of the internal housing to form a space for containing process gases for use in the internal housing. The internal housing also has first piping for transferring process gases or liquids, and second piping, integral to the internal housing and the outer encasement, also for transferring process gases to the space. The apparatus further includes an O-ring, and a tube connected to the first or second piping. The tube has a flange shaped to hold the O-ring against the piping and against only an outer portion of the flange. The apparatus further includes a fastening mechanism tightly connecting the piping and the flange to sandwich the O-ring, and leakage of process gases or liquids from a joint of the piping, the O-ring, and the flange is prevented.
The present invention achieves these benefits in the context of an oxidizing furnace. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.